Switch control circuit including multipin to set dead time information and/or protection mode

ABSTRACT

A switch control circuit includes a first pin connected to a first voltage, and a second pin connected to another end of a first resistor including an end connected to the first pin and a first capacitor. In the switch control circuit, at least two of first dead time information, second dead time information, and a protection mode are set by using a multi-voltage of the second pin. The first dead time information is information about a dead time of a first switch and a second switch controlling power supply, the second dead time information is information about a dead time for synchronous rectification, and the protection mode includes an auto-restart mode and a latch mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/272,580 filed May 8, 2014. The entire disclosure of which isincorporated herein by reference.

BACKGROUND

(a) Field

Embodiments relates to a switch control circuit and a power supplydevice including the same.

(b) Description of the Related Art

A general controller includes pins corresponding to required functions.For example, a pin for setting a dead time, a pin for setting aprotection mode, and a pin for remote controlling are provided in thecontroller.

When the number of required functions is increased, the number of pinsis increased, and thus a size of a control IC is increased and aproduction cost is increased.

SUMMARY

Embodiments have been made in an effort to provide a switch controlcircuit and a power supply device minimizing an increase in number ofpins and size of a control IC through embodiments.

An embodiment provides a switch control circuit comprising: a first pinconfigured to be connected to a first voltage, and a second pinconfigured to be connected to another end of a first resistor includingan end connected to the first pin and a first capacitor, wherein atleast two of first dead time information, second dead time information,and a protection mode are set by using a multi-voltage of the secondpin. The first dead time information may be information about a deadtime of a first switch and a second switch controlling power supply, thesecond dead time information may be information about a dead time forsynchronous rectification, and the protection mode may include anauto-restart mode and a latch mode.

When the multi-voltage starts to occur and reaches an initializationvoltage, the switch control circuit is initialized and performs at leastone of setting of a first dead time and setting of a second dead timeduring an initialization period.

After the initialization period is ended, a protection mode is setaccording to a level of the multi-voltage when the multi-voltage is in asteady state.

The first switch is connected to the second pin and performs a switchingoperation by a remote control signal.

A multi-voltage occurs when the first switch is turned-off, and themulti-voltage is pulled-down when the first switch is turned-on.

The switch control circuit further comprises a biasing circuitconfigured to supply the first voltage to the first pin when a sourcevoltage supplied to the switch control circuit is in a steady state.

The switch control circuit further comprises an initialization unitconfigured to count an initialization period by using a count clocksignal from a time at which the multi-voltage reaches an initializationvoltage.

The initialization unit includes a first counter configured to beenabled at a time at which the multi-voltage reaches the initializationvoltage and including a plurality of output ends having a leveldetermined according to a count result using the count clock signal, andthe initialization unit determines an end of the initialization periodaccording to an output of the output end corresponding to theinitialization period among the plurality of output ends.

A first period during which the multi-voltage is changed from a firstthreshold voltage to a second threshold voltage is counted to set thefirst dead time.

The switch control circuit further comprises a first comparatorconfigured to generate a first comparison signal according to acomparison result of the multi-voltage and the first threshold voltage,a second comparator configured to generate a second comparison signalaccording to a comparison result of the multi-voltage and the secondthreshold voltage, and a second counter configured to be enabled basedon the first comparison signal and reset based on the second comparisonsignal to count the first period.

The switch control circuit further comprises a first D-flip-flopconfigured to be reset by an inverted comparison signal obtained byreversing the first comparison signal, a second D-flip-flop configuredto be synchronized with an inverted output signal of the firstD-flip-flop to output an output signal of an enable level, and reset bythe second comparison signal, and a first logic gate configured toperform a logical operation of the output signal and the firstcomparison signal of the second D-flip-flop to generate a first countenable signal.

The second counter is synchronized with a rising edge of the first countenable signal to be enabled and reset after a first delay period from afalling edge time of the first count enable signal.

The switch control circuit further comprises a second logic gateconfigured to perform a logical operation of an inverted first countenable signal and a signal obtained by delaying the first count enablesignal by a second delay period to generate a first register readsignal.

The switch control circuit further comprises a first register configuredto include a plurality of input ends connected to a plurality of outputends of a second counter and be synchronized with the first registerread signal to store inputs of the plurality of input ends. Theplurality of output ends of the second counter have a level according toa count result.

A second period during which the multi-voltage is changed from a secondthreshold voltage to a first threshold voltage is counted to set asecond dead time. The switch control circuit further comprises a firstcomparator configured to generate a first comparison signal according toa comparison result of the multi-voltage and the first thresholdvoltage, a third D-flip-flop configured to generate a second countenable signal at a high level at a first time delayed from a time atwhich the multi-voltage reaches the second threshold voltage by a firstdelay period, and be reset by an inverted comparison signal obtained byinverting the first comparison signal, and a second counter configuredto be reset at the first time, and synchronized with a rising edge ofthe second count enable signal to count the second period.

The switch control circuit further comprises a third logic gateconfigured to perform a logical operation of an inverted second countenable signal and a signal obtained by delaying the second count enablesignal by a second delay period to generate a second register readsignal.

The switch control circuit further comprises a second registerconfigured to include a plurality of input ends connected to a pluralityof output ends of the second counter and be synchronized with the secondregister read signal to store inputs of the plurality of input ends. Theplurality of output ends of the second counter have a level according toa count result.

The switch control circuit further comprises a sink current sourceconfigured to be connected to a second pin, and a second switchconfigured to be connected between the sink current source and a ground.The second switch is synchronized to be turned-on at a time at which themulti-voltage reaches the second threshold voltage, and synchronized tobe turned-off at a time at which the multi-voltage reaches the firstthreshold voltage.

The switch control circuit further comprises a sink current sourceconfigured to be connected to the second pin, and the second switchconfigured to be connected between the sink current source and a ground.The second switch is turned-on at a time at which the multi-voltagereaches an initialization voltage, and turned-off at a time at which themulti-voltage reaches a first threshold voltage. The initializationvoltage is a voltage controlling an initialization start of the switchcontrol circuit, and the first threshold voltage is a voltagecontrolling the first dead time information and the second dead timeinformation.

A diode may be connected between the first pin and the end of the firstresistor. Another embodiment provides A power supply device comprising:a first switch and a second switch configured to be connected in seriesbetween an input voltage and a primary side ground, a transformerconfigured to include a primary side wire connected between the inputvoltage and a node connected to the first switch and the second switchand a secondary side wire, a first synchronous rectification switchconfigured to rectify a current flowing through a first wire of asecondary side, a second synchronous rectification switch configured torectify a current flowing through a second wire of the secondary side, aswitch control circuit configured to include a first pin connected to afirst voltage and a second pin, and set at least two of first dead timeinformation, second dead time information, and a protection mode byusing a multi-voltage of the second pin, a first resistor configured tobe connected between the first pin and the second pin, and a firstcapacitor configured to be connected to the second pin.

The first dead time information may be information about a dead time ofthe first switch and the second switch, the second dead time informationmay be information about a dead time of the first synchronousrectification switch and the second synchronous rectification switch,and the protection mode includes an auto-restart mode and a latch mode.

The power supply device further comprises the first switch configured tobe connected to the second pin. The first switch performs a switchingoperation by a remote control signal.

The power supply device further comprises a sink current sourceconfigured to be connected to the second pin, and the second switchconfigured to be connected between the sink current source and theground.

The switch control circuit sets a first dead time by counting a firstperiod during which the multi-voltage is changed from a first thresholdvoltage to a second threshold voltage.

The switch control circuit sets a second dead time by counting a secondperiod during which the multi-voltage is changed from a second thresholdvoltage to a first threshold voltage.

The power supply device further may comprise a diode configured to beconnected between the first pin and the first resistor.

According to the embodiments, there are provided a switch controlcircuit minimizing an increase in number of pins and size of a controlIC, and a power supply device including the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a power supply device according to anembodiment.

FIG. 2 is a view showing a portion of a switch control circuit accordingto the embodiment.

FIG. 3 is a view showing another portion of the switch control circuitaccording to the embodiment.

FIG. 4 is a waveform diagram showing waveforms of signals according tothe embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the embodiments will be described in detail with referenceto the accompanying drawings so that those skilled in the art may easilypractice the embodiment. As those skilled in the art would realize, thedescribed embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the invention. Thedrawings and description are to be regarded as illustrative in natureand not restrictive. Like reference numerals designate like elementsthroughout the specification.

Throughout this specification and the claims that follow, when it isdescribed that an element is “coupled” to another element, the elementmay be “directly coupled” to the other element or “electrically coupled”to the other element through a third element. In addition, unlessexplicitly described to the contrary, the word “comprise” and variationssuch as “comprises” or “comprising”, will be understood to imply theinclusion of stated elements but not the exclusion of any otherelements.

A multifunctional pin of a switch controller according to an embodimentis connected to electric elements so that at least two controlinformation are set. For example, a resistor, a capacitor, and aswitching element may be electrically connected to the multifunctionalpin. Control information may be set through a voltage of themultifunctional pin. Additionally, a diode may be connected between thecapacitor and the resistor.

Control information is information required to control a switchingoperation, and may include at least two of remote control information,information for setting a protection mode, information about a dead timebetween primary side switches, and information about a dead time forsecondary synchronous rectification. Secondary synchronous rectificationis performed through a first synchronous rectification switch and asecond synchronous rectification switch connected to a secondary wire.Remote control information may be control information shutting down oractivating a power supply device.

FIG. 1 is a view showing a power supply device according to anembodiment.

The power supply device shown in FIG. 1 is embodied by a half-bridge LLCresonance type converter (hereinafter, converter), but a converter typeto which the embodiment is capable of being applied is not limitedthereto. The half-bridge LLC resonance type converter will be describedas an example to describe setting of control information.

A power supply device 1 includes a first switch Q1, a second switch Q2,a transformer 20, a gate driving circuit 60, a first synchronousrectification switch SR1, a second synchronous rectification switch SR2,and a switch control circuit 10.

Body diodes BD1 and BD2 are formed between a drain and a source of thefirst switch Q1 and between the drain and the source of the secondswitch Q2, respectively.

The second switch Q2 and the first switch Q1 are connected in seriesbetween an input voltage Vin and a primary side ground, and the secondswitch Q2 and the first switch Q1 alternately perform the switchingoperation. The second switch Q2 is turned-off, the first switch Q1 isturned-on after a first dead time, the first switch Q1 is turned-off,and the second switch Q2 is turned-on after the first dead time.

The drain of the second switch Q2 is connected to the input voltage Vin,the source of the second switch Q2 and the drain of the first switch Q1are connected in a node Nd, and the source of the first switch Q1 isconnected to the primary side ground. Gate voltages VG1 and VG2 aresupplied to gates of the second switch Q2 and the first switch Q1. Thefirst switch Q1 and the second switch Q2 are alternately switched, andpower supply is controlled according to the switching operation. Forexample, power supply is increased as switching frequencies of the firstswitch Q1 and the second switch Q2 are reduced. Power supply is reducedas a switching frequency is increased.

A capacitor Cr, a primary side wire W11 of a transformer 20, and aninductor Lr are connected in series between the input voltage Vin andthe node Nd. A resonance occurs among the capacitor Cr, the primary sidewire W11, and the inductor Lr. A current Iin inputted to a primary sideis controlled by a sine wave due to the resonance.

A wire W21 and a wire W22 are insulating-coupled with the primary sidewire W11 at a predetermined wiring ratio in a secondary side of thetransformer 20. The first synchronous rectification switch SR1 isconnected to an end of the secondary side wire W21. A body diode BD3 isformed between a drain and a source of the first synchronous currentswitch SR1. The second synchronous rectification switch SR2 is connectedto an end of the secondary side wire W22. A body diode BD4 is formedbetween a drain and a source of the second synchronous rectificationswitch SR2.

A turn-on time of the first synchronous rectification switch SR1 (or thesecond synchronous rectification switch SR2) is determined according toa conduction time of the body diode BD3 (or the body diode BD4). Aturn-off time of the first synchronous rectification switch SR1 (or thesecond synchronous rectification switch SR2) is determined based on theresult obtained by counting turn-on periods during a prior switchingcycle.

For example, after the body diode BD3 (or BD4) is conducted by aswitching operation of the primary side, a conduction period is counted.Thereafter, when the body diode BD3 (or BD4) is conducted again, thefirst synchronous rectification switch SR1 (or SR2) is turned-on, andthe turn-on period of the first synchronous rectification switch SR1 (orSR2) is set based on the prior conduction period of the body diode BD3(or BD4). In this case, the turn-on period may be set to a period thatis shorter than the counted prior conduction period of the body diode bya predetermined margin.

When a set turn-on period elapses, the first synchronous rectificationswitch SR1 is turned-off. Moreover, the conduction period of the bodydiode BD3 (or BD4) is counted during a current switching cycle of thefirst synchronous rectification switch SR1.

When the body diode BD3 (or BD4) is conducted again, the firstsynchronous rectification switch SR1 (or SR2) is turned-on, and theturn-on period of the first synchronous rectification switch SR1 (orSR2) is set based on the conduction period of the body diode BD3 (orBD4) during the prior switch cycle. When the set turn-on period elapses,the first synchronous rectification switch SR1 is turned-off. Moreover,the conduction period of the body diode BD3 (or BD4) is counted duringthe current switching cycle of the first synchronous rectificationswitch SR1.

The switching operation of the first synchronous rectification switchSR1 (or SR2) may be controlled by repeating the aforementionedoperation.

The conduction period of the body diode BD3 (or BD4) may be seen bysensing both end voltages of the first synchronous rectification switchSR1 (or SR2). When the body diode BD3 (or BD4) is conducted, the bothend voltages become low voltages that are close to a zero voltage. Whenthe current flowing the body diode BD3 (or BD4) is reduced to 0 afterresonance, the body diode BD3 blocks an inverse direction current andthe both end voltages become high voltages.

Since the both end voltages of the first synchronous rectificationswitch SR1 and the both end voltages of the second synchronousrectification switch SR2 are symmetrical to each other, when any oneboth end voltage is obtained, other both end voltages are capable ofbeing estimated. Therefore, in the embodiment, measurement of only theboth end voltages of the first synchronous rectification switch SR1 willbe described. In FIG. 1, a resistor R8 and a resistor R9 are connectedin series between a drain of the first synchronous rectification switchSR1 and a secondary side ground. A voltage SRD1 of the node at which thetwo resistors are connected is supplied through a pin P5 to the switchcontrol circuit 10. However, the embodiment is not limited thereto.

The aforementioned controlling of the first and second synchronousrectification switches SR1 and SR2 is performed by the switch controlcircuit 10. The switch control circuit 10 includes a pin P3, a pin P4,and the pin P5. A gate voltage SRG1 is outputted through the pin P3, agate voltage SRG2 is outputted through the pin P4, and the voltage SRD1is inputted through the pin P5.

The source of the first synchronous rectification switch SR1 isconnected to the secondary side ground, and the drain is connected to anend of the secondary side wire W21. The gate voltage SRG1 is inputted tothe gate. A resistor R10 is connected between the gate and the source ofthe first synchronous rectification switch SR1. The source of the secondsynchronous rectification switch SR2 is connected to the secondary sideground, and the drain is connected to an end of the secondary side wireW22. The gate voltage SRG2 is inputted to the gate. A resistor R11 isconnected between the gate and the source of the second synchronousrectification switch SR2.

Another end of the secondary side wire W21 and another end of the wireW22 are connected to an output node No. A capacitor C3 and a capacitorC4 are connected between the output node No and the secondary sideground. A voltage of the output node No is an output voltage Vo.

The current flowing through the first synchronous rectification switchSR1 to the secondary side wire W21 is rectified and flows to thecapacitors C3 and C4. The current flowing through the second synchronousrectification switch SR2 to the secondary side wire W22 is rectified andflows to the capacitors C3 and C4 to generate the output voltage Vo.

A feedback voltage VFB between two resistors R12 and R13 connected inseries between the output node No and the secondary side ground isinputted through a pin P9 to the switch control circuit 10. The feedbackvoltage VFB is information about the output voltage Vo. The switchcontrol circuit 10 determines the switching frequency according toincreasing or decreasing of the feedback voltage VFB. For example, whenthe feedback voltage VFB is increased, the switching frequency isincreased to reduce the current supplied to a load. When the feedbackvoltage VFB is decreased, the switching frequency is reduced to increasethe current supplied to the load.

The switch control circuit 10 receives remote control information byusing a voltage of a multifunctional pin P10 (hereinafter, multi-voltageVM). The switch control circuit 10 sets information for setting aprotection mode, information about the first dead time between thesecond switch Q2 and the first switch Q1, and information about a seconddead time between the first synchronous rectification switch SR1 and thesecond synchronous rectification switch SR2. A diode D1, a resistor R1,a capacitor C2, and a switch S1 are connected to the multifunctional pinP10.

The switch control circuit 10 further includes a plurality of pins inaddition to the multifunctional pin P10. For example, the switch controlcircuit 10 may further include a pin P1 to which a first driving voltagePDRV1 is outputted, a pin P2 to which a second driving voltage PDRV2 isoutputted, a pin P7 to which a source voltage VDD is supplied, a pin P8connected to a bias voltage VB for charging the capacitor C2, and a pinP6 for sensing a primary side current. The embodiment is not limitedthereto, and the switch control circuit 10 may further include a pinother than the pins shown in FIG. 1.

The gate driving circuit 60 includes a secondary side wire W23, twoprimary side wires W12 and W13, four resistors R2 to R5, and two diodesD2 and D3.

The first driving voltage PDRV1 is inputted to an end of the secondaryside wire W23, and the second driving voltage PDRV2 is inputted toanother end of the secondary side wire W23. The resistor R2 and thediode D2 are connected in parallel between an end of the primary sidewire W12 and the gate of the second switch Q2. Another end of theprimary side wire W12 is connected to an end of the resistor R3 and thenode Nd. The resistor R2, the resistor R3, and an anode of the diode D2are connected to the gate of the second switch Q2. The resistor R4 andthe diode D3 are connected in parallel between an end of the primaryside wire W13 and the gate of the first switch Q1. Another end of theprimary side wire W13 is connected to an end of the resistor R5 and theprimary side ground. The resistor R4, the resistor R5, and an anode ofthe diode D3 are connected to the gate of the first switch Q1.

The first switch Q1 performs a switching operation according to the gatevoltage VG1, and the second switch Q2 performs the switching operationaccording to the gate voltage VG2. Since the first switch Q1 and thesecond switch Q2 are an n channel transistor, an enable level of each ofthe gate voltage VG1 and the gate voltage VG2 is a high level, and adisable level is a low level.

When the first driving voltage PDRV1 has the high level and the seconddriving voltage PDRV2 has the low level, the current of the primary sidewire W12 flows through the resistor R3 and the diode D2, and the currentof the primary side wire W13 flows through the resistor R4 and theresistor R5. Then, the gate voltage VG1 becomes a high level voltagecapable of turning-on the first switch Q1, and thus the first switch Q1is turned-on. The gate voltage VG2 becomes a voltage that is lower thanthe source voltage of the second switch Q2, and thus the second switchQ2 is turned-off.

When the second driving voltage PDRV2 is the high level and the firstdriving voltage PDRV1 is the low level, the current of the primary sidewire W12 flows through the resistor R2 and the resistor R3, and thecurrent of the primary side wire W13 flows through the resistor R5 andthe diode D3. Then, the gate voltage VG2 becomes the high level voltagecapable of turning-on the second switch Q2, and thus the second switchQ2 is turned-on. The gate voltage VG1 becomes a voltage that is lowerthan the source voltage of the first switch Q1, and thus the firstswitch Q1 is turned-off.

When the input current Iin flows through the inductor Lr, the current isinduced to a secondary side wire W24 to generate a sensing voltage VCS.For example, when the input current Iin flows in a direction toward thenode Nd due to resonance, the current of the secondary side wire W24flows through a resistor R7 and a resistor R6 to the secondary sideground. Then, a positive sensing voltage VCS corresponding to the inputcurrent Iin occurs. When the input current Iin flows in a dischargedirection from the node Nd due to resonance, the current of thesecondary side wire W24 flows from the secondary side ground through theresistor R6 and the resistor R7. Then, a negative sensing voltage VCScorresponding to the input current Iin occurs.

The sensing voltage VCS may be supplied through the pin P6 to the switchcontrol circuit 10, and the switch control circuit 10 may sense anovercurrent by using the sensing voltage VCS.

A capacitor C1 is connected to the pin P8, and a ripple of the biasvoltage VB is filtered by the capacitor C1.

An anode of the diode D1 is connected to the bias voltage VB, and acathode of the diode D1 is connected to an end of the resistor R1.Another end of the resistor R1 is connected to the pin P10. Thecapacitor C2 is connected between the pin P10 and the secondary sideground.

In FIG. 1, the diode D1, the resistor R1, and the capacitor C2 areconnected in series, but the embodiment is not limited thereto. Theresistor R1 and the capacitor C2 may be connected in series without thediode D1. Setting of the protection mode relates to whether the diode D1is connected or not. A detailed configuration will be described below.

A drain of the switch S1 is connected to the pin P10, a source of theswitch S1 is connected to the secondary side ground, and a remotecontrol signal RNF is applied to a gate of the switch S1.

When the remote control signal RNF has an enable level, for example, alow level, the switch S1 is turned-off, and thus the capacitor C1 ischarged. The multi-voltage VM is increased by charging the capacitor C1to trigger a start-up operation. When the remote control signal RNF hasa disable level, for example, a high level, the switch S1 is turned-on,and thus the multi-voltage VM is pulled-down to a zero voltage. Then,the switch control circuit 10 is not initialized, and the power supplydevice 1 does not start-up. Further, when the remote control signal RNFis a high level during the operation of the switch control circuit 10,the switch control circuit 10 stops the switching operation of the firstswitch Q1 and the second switch Q2. Then, the power supply device 1 isshut-down.

The switch control circuit 10 may count a period during which themulti-voltage VM is increased from a first threshold voltage VTH1 to asecond threshold voltage VTH2, and set the counted period as the firstdead time.

Further, the switch control circuit 10 may count a period during whichthe multi-voltage VM is decreased from the second threshold voltage VTH2to the first threshold voltage VTH1 with a predetermined slope, and setthe counted period as the second dead time.

Moreover, the switch control circuit 10 may set the protection modeaccording to a steady state level of the multi-voltage VM. Theprotection mode may be an auto-restart mode or a latch mode. Theauto-restart mode is a protection mode where an operation of the switchcontrol circuit is re-started after a predetermined period from aprotection operation is activated. The latch mode is a protection modewhere the protection operation is activated and maintained. In the latchmode, the protection mode may be released by a reset operation wherebythe input voltage Vin of the power supply device 1 is blocked and thensupplied again.

The switch control circuit 10 may be initialized when the multi-voltageVM reaches a predetermined initialization voltage to set the first deadtime and the second dead time during a predetermined initializationperiod. Further, the switch control circuit 10 may set the protectionmode according to a level of the multi-voltage VM of a steady stateafter the initialization period has ended. Hereinafter, the switchcontrol circuit according to the embodiment will be described in detailwith reference to FIG. 2.

FIG. 2 is a view showing a portion of the switch control circuitaccording to the embodiment.

FIG. 3 is a view showing another portion of the switch control circuitaccording to the embodiment.

FIG. 2 shows only constitutions describing the embodiment amongconstitutions of the switch control circuit 10, but the embodiment isnot limited thereto.

A comparator 11 generates a signal VDDG according to a comparison resultof the source voltage VDD and reference voltages (8/10 V). According toa hysteresis characteristic of the comparator 11, the comparator 11outputs the signal VDDG at a high level when the source voltage VDDstarts to be increased and reaches 10 V or more. After the sourcevoltage VDD is 10 V or more, when the source voltage VDD is 8 V or more,the high level is maintained. When the source voltage VDD is a voltageof less than 8 V, the comparator 11 outputs the signal VDDG at a lowlevel to show an under-voltage state. The reference voltages of 8 V and10 V are values set to describe the embodiment, but the embodiment isnot limited thereto.

A biasing circuit 33 generates the bias voltage VB when the sourcevoltage VDD is in a steady state. For example, the biasing circuit 33may be activated by the signal VDDG at the high level to generate thebias voltage VB by using the source voltage VDD. A current charging thecapacitor C2 may be supplied when the bias voltage VB is supplied in apredetermined voltage (e.g., 5 V).

A comparator 13 generates a signal VMS according to a comparison resultof the multi-voltage VM and reference voltages (0.5/1.5 V). According toa hysteresis characteristic of the comparator 13, the comparator 13outputs the signal VMS at a high level when the multi-voltage VM startsto be increased and reaches 1.5 V or more. After the multi-voltage VM is1.5 V or more, when the multi-voltage VM is 0.5 V or more, the highlevel is maintained. When the multi-voltage VM is a voltage of less than0.5 V, the comparator 13 outputs the signal VMS at a low level. Thereference voltages of 0.5 V and 1.5 V are values set to describe theembodiment, but the embodiment is not limited thereto.

An initialization unit 100 counters the initialization period by using acount clock signal HFCLK from a time at which the multi-voltage VMreaches the initialization voltage, and enables an initialization signalINIT controlling setting of the first dead time and setting of thesecond dead time during the initialization period. After theinitialization period is ended, the initialization unit 100 enables aninitialization end signal INIT_END and disables the initializationsignal INIT.

The initialization unit 100 starts to count the initialization periodwhen the multi-voltage VM reaches a predetermined reference voltagewhile the source voltage VDD is in the steady state, not theunder-voltage state. When the source voltage VDD is in the under-voltagestate, counting of the initialization period does not start. Further,the initialization unit 100 maintains a counting operation of theinitialization period when the source voltage VDD is in the steadystate. When the source voltage VDD is the under-voltage state duringcounting, a counting result is reset regardless of the multi-voltage VM.

The initialization unit 100 includes two AND gates 101 and 105, aninverter 102, a first counter 103, and an SR latch 104.

The AND gate 101 performs a logical AND operation of the signal VDDG andthe signal VMS to determine an output. When both two input signals areat a high level, the output of the AND gate 101 has a high level. When ahigh level as an enable level is inputted to an enable end ENA of thefirst counter 103, the first counter 103 starts a counting operation byusing the count clock signal HFCLK.

The inverter 102 is connected to an output end of the AND gate 101,inverts the output of the AND gate 101, and outputs the inverted output.When a high level is inputted to a reset end RST of the first counter103, the first counter 103 resets a counting result. For example, whenat least one of the signal VDDG and the signal VMS is at a low level,the counting result of the operated first counter 103 is reset.

The first counter 103 includes a plurality of output ends D0-Dn. Levelsof a plurality of output ends D0-Dn are determined according to thecounting result of the first counter 103. The output of an appropriateoutput end among a plurality of output ends D0-Dn may be selectedaccording to the initialization period. FIG. 1 shows that the output ofan n-th output end Dn corresponds to the initialization period, but theembodiment is not limited thereto.

The SR latch 104 enables the initialization end signal INTEND accordingto the output of the first counter 103 and outputs an inverted outputsignal QB for disabling the initialization signal INT. A set end S ofthe SR latch 104 is connected to the output of the first counter 103,and a reset end of the SR latch 104 is connected to an output of theinverter 102. The initialization end signal INT_END is outputted throughan output end Q of the SR latch 104, and the inverted output signal QBis outputted through an inverted output end Q.

Since the output of the inverter 102 is a high level before themulti-voltage VM is increased, the inverted output signal QB is a highlevel and the initialization end signal INT_END is a low level. When theoutput of the inverter 102 is a low level due to an increase of themulti-voltage VM, outputs of the output end Q and the inverted outputend Q are determined according to the input of the set end S. Forexample, when the output of the output end Dn of the first counter 103is a high level, the initialization end signal INT_END is a high leveland the inverted output signal QB is a low level.

The AND gate 105 performs a logical AND operation of the output of theAND gate 101 and the inverted output signal QB to generate theinitialization signal INT. When both two inputs are a high level, theAND gate 101 generates the initialization signal INT of the enablelevel.

A sink current source 12 may be connected to the pin P10 to control adecreasing slope of the multi-voltage VM. A switch S2 is connectedbetween the sink current source 12 and the secondary side ground. Whenthe switch S2 is turned-on by an output of an OR gate 17, themulti-voltage VM is decreased by a current ID of the sink current source12. The decreasing slope of the multi-voltage VM may be adjustedaccording to a level of the current ID.

A comparator 14 generates a first comparison signal CM1 according to acomparison result of the multi-voltage VM and the first thresholdvoltage VTH1. A comparator 15 generates a second comparison signal CM2according to a comparison result of the multi-voltage VM and the secondthreshold voltage VTH2. A comparator 16 generates a protection modesignal PMS setting the protection mode according to a comparison resultof the multi-voltage VM and a third threshold voltage VTH3.

The multi-voltage VM is inputted to a non-inverting terminal (+) of eachof the comparator 14, the comparator 15, and the comparator 16. Thefirst to third threshold voltages VTH1-VTH3 are inputted to invertingterminals (−) of the comparator 14, the comparator 15, and thecomparator 16, respectively.

FIG. 2 shows that the first threshold voltage VTH1 is 1 V, the secondthreshold voltage VTH2 is 3 V, and the third threshold voltage VTH3 is4.8 V, but is just an example for description, but the embodiment is notlimited thereto. Moreover, in the embodiment, the bias voltage VB is setto 5 V.

An inverter 21 inverts the first comparison signal CM1 to generate aninverted comparison signal CMB1.

D-flip-flops 18, 19, 25, and 28 include a clock terminal CK, and aresynchronized with a rising edge of an input of the clock terminal tooutput an input of an input end D.

The bias voltage VB is inputted to the input end D of the D-flip-flop18. The D-flip-flop 18 outputs an output signal MR of a high levelaccording to a high level of the input end D through the output end Qand outputs an inverted output signal MRB of a low level through theinverted output end Q in synchronization with a rising edge of theinitialization signal INT. The inverted comparison signal CMB1 isinputted to a clear end CLR of the D-flip-flop 18. The D-flip-flop 18resets the output signal MR at a low level and generates the invertedoutput signal MRB of a high level according to the inverted comparisonsignal CMB1 of the high level as the enable level.

The bias voltage VB is inputted to the input end D of the D-flip-flop19. The D-flip-flop 19 outputs an output signal DQ1 of a high levelthrough the output end Q in synchronization with a rising edge of theinverted output signal MRB of the D-flip-flop 18. The second comparisonsignal CM2 is inputted to a clear end CLR of the D-flip-flop 19. TheD-flip-flop 19 resets the output signal DQ1 at a low level according tothe second comparison signal CM2 of a high level as the enable level.

An AND gate 20 performs a logical AND operation of the output signal DQ1of the D-flip-flop 19 and the first comparison signal CM1 to generate afirst count enable signal CE1. When both two inputs have a high level,the AND gate 20 generates the first count enable signal CE1 of a highlevel.

A delay unit 22 and a logic gate 23 constitute a pulse generator. Thedelay unit 22 delays the first count enable signal CE1 by apredetermined period and outputs the first count enable signal CE1. Aninput end of the logic gate 23 is an inverting input end, and the inputend of the logic gate 23 to which the first count enable signal CE1 isinputted is the inverting input end. The logic gate 23 performs alogical AND operation of an inverted first count enable signal CE1 andthe output of the delay unit 22 to generate a first register read signalRR1. For example, the logic gate 23 is synchronized with a falling edgeof the inverted first count enable signal CE1 to generate the firstregister read signal RR1 as a short pulse having a high level during adelay period.

A delay unit 24 delays the first register read signal RR1 by apredetermined period and outputs a count reset signal CR.

The bias voltage VB is inputted to an input end D of a D-flip-flop 25.D-flip-flop 25 outputs a second count enable signal CE2 of a high levelthrough the output end Q in synchronization with a rising edge of thedelayed first register read signal RR1.

The inverted comparison signal CMB1 is inputted to a clear end CLR ofthe D-flip-flop 25. The D-flip-flop 25 resets the second count enablesignal CE2 at a low level according to the inverted comparison signalCMB1 of a high level as the enable level.

A delay unit 26 and a logic gate 27 constitute a pulse generator. Thedelay unit 26 delays the second count enable signal CE2 by apredetermined period and outputs the second count enable signal CE2. Aninput end of the logic gate 27 is an inverting input end, and the inputend of the logic gate 27 to which the second count enable signal CE2 isinputted is the inverting input end. The logic gate 27 performs alogical AND operation of an inverted second count enable signal CE2 andthe output of the delay unit 26 to generate a second register readsignal RR2. For example, the logic gate 27 is synchronized with afalling edge of the inverted second count enable signal CE2 to generatethe second register read signal RR2 as a short pulse having a high levelby a delay period.

An OR gate 29 outputs a logical OR operation result of the first andsecond count enable signals CE1 and CE2. For example, when at least oneof the first and second count enable signals CE1 and CE2 is a highlevel, the output of the OR gate 29 has a high level.

When a high level as the enable level is inputted to an enable end ENAof a second counter 30, the second counter 30 starts a countingoperation by using the count clock signal HFCLK. When a high level isinputted to a reset end RST of the second counter 30, the second counter30 resets a counting result. For example, when a count reset signal CRhas a high level, the counting result of the second counter 30 is reset.

The second counter 30 includes a plurality of output ends D0-Dn. Thelevels of a plurality of output ends D0-Dn are determined according tothe counting result of the second counter 30. A count signal CNT isgenerated by a combination of the levels of a plurality of output endsD0-Dn. A plurality of output ends D0-Dn are connected to a plurality ofinput ends of a first register 31 and a second register 32. Forconvenience of description, a plurality of input ends of the first andsecond registers 31 and 32 are designated by the same reference numeralsas a plurality of output ends of the second counter 30.

The first register 31 stores the first dead time between the firstswitch Q1 and the second switch Q2 of the primary side. The firstregister 31 includes a clock end CK, and is synchronized with a risingedge of the clock end CK to store the count signal CNT inputted to aplurality of input ends D0-Dn. The first register read signal RR1 isinputted to the clock end CK of the first register 31. The firstregister 31 outputs first dead time information PSD through a pluralityof output ends Q0-Qn.

The second register 32 stores the second dead time between the firstsynchronous rectification switch SR1 and the second synchronousrectification switch SR2 of the secondary side. The second register 32includes the clock end CK, and is synchronized with the rising edge ofthe clock end CK to store the count signal CNT inputted to a pluralityof input ends D0-Dn. The second register read signal RR2 is inputted tothe clock end CK of the second register 32. The second register 32outputs second dead time information SSD through a plurality of outputends Q0-Qn.

The bias voltage VB is inputted to an input end D of a D-flip-flop 28.The D-flip-flop 28 outputs a multi-discharge signal MD of a high levelthrough the output end Q in synchronization with a rising edge of thefirst register read signal RR1. The second register read signal RR2 isinputted to a clear end CLR of the D-flip-flop 28. The D-flip-flop 28resets the multi-discharge signal MD at a low level according to thesecond register read signal RR2 of a high level as the enable level.

The OR gate 17 receives the multi-discharge signal MD and the outputsignal MR of the D-flip-flop 18 and performs a logical OR operation togenerate a gate voltage VG. When at least one of two inputs is a highlevel, the OR gate 17 generates the gate voltage VG of a high level.When the switch S2 is turned-on by the gate voltage VG of a high level,the multi-voltage VM is reduced by discharging.

FIG. 2 shows that the bias voltage VB is inputted to the input ends D ofthe D-flip-flops 18, 19, 25, and 28, but the voltage of the input end Dis not limited to the bias voltage VB and may be another voltage of ahigh level.

Referring to FIG. 3, the switch control circuit 10 further includes anoscillator 200, a protection circuit 300, a driving signal generationunit 400, and a synchronous rectification controller 500.

The oscillator 200 receives the feedback voltage VFB, and generates aclock signal CLK determining the switching frequency according to thefeedback voltage VFB. For example, the frequency of the clock signal CLKis increased to increase the switching frequency according to anincrease in feedback voltage VFB. On the contrary, the frequency of theclock signal CLK is decreased to reduce the switching frequencyaccording to a decrease in feedback voltage VFB.

The protection circuit 300 sets the protection mode based on theprotection mode signal PMS, and senses the sensing voltage VCS tocontrol a protection operation. For example, the protection circuit 300may generate a protection signal PS of the enable level when theovercurrent is sensed.

The driving signal generation unit 400 receives the clock signal CLK,first dead time information PSD, and the protection signal PS, andgenerates the first driving voltage PDRV1 and the second driving voltagePDRV2 based on the clock signal CLK and first dead time information PSD.The driving signal generation unit 400 may not generate the firstdriving voltage PDRV1 and the second driving voltage PDRV2 according tothe protection signal PS of the enable level.

For example, the driving signal generation unit 400 increases the firstdriving voltage PDRV1 at a high level at a time delayed from a risingedge of the clock signal CLK by the first dead time according to firstdead time information PSD and decreases the second driving voltage PDRV2at a low level at the rising edge of the clock signal CLK. The drivingsignal generation unit 400 increases the second driving voltage PDRV2 ata high level at the time delayed from a falling edge of the clock signalCLK by the first dead time according to first dead time information PSDand decreases the first driving voltage PDRV1 at a low level at thefalling edge of the clock signal CLK.

The synchronous rectification controller 500 receives the voltage SRD1corresponding to both end voltages of the first synchronousrectification switch SR1 senses the conduction time of the body diodeBD3 by using the voltage SRD1, and is synchronized with the conductiontime to generate a gate voltage SRG1 of a high level turning-on thefirst synchronous rectification switch SR1.

The synchronous rectification controller 500 maintains the gate voltageSRG1 at a high level during the turn-on period set based on theconduction period of the body diode BD3 counted by using the voltageSRD1 during the prior switching cycle, and counts the conduction periodof the body diode BD3 during the current switching cycle by using thevoltage SRD1.

Further, the synchronous rectification controller 500 estimates both endvoltages of the second synchronous rectification switch SR2 by using thevoltage SRD1. The synchronous rectification controller 500 may flip thevoltage SRD1 based on a zero voltage and then perform level shifting toestimate both end voltages of the second synchronous rectificationswitch SR2.

The synchronous rectification controller 500 determines a turn-on timeof the second synchronous rectification switch SR2 by using both endvoltages of the estimated second synchronous rectification switch SR2,and generates the gate voltage SRG2 of a high level.

The synchronous rectification controller 500 counts the conductionperiod of the body diode BD4 by using the estimated both end voltages ofthe second synchronous current switch SR2 during the prior switchingcycle. The synchronous rectification controller 500 maintains the gatevoltage SRG2 at a high level during a turn-on period set based on thecounted period. Further, the synchronous rectification controller 500counts the conduction period of the body diode BD4 by estimating theboth end voltages of the second synchronous rectification switch SR2during the current switching cycle.

Hereinafter, an operation of the switch control circuit according to theembodiment will be described with reference to FIG. 4.

Specifically, setting of the first dead time, the second dead time, andthe protection mode will be described with reference to FIG. 4.

FIG. 4 is a waveform diagram showing waveforms of signals according tothe embodiment.

Hereinafter, it is assumed that the signal VDDG has a high level in thedescription of the operation with reference to FIG. 4. The remotecontrol signal RNF has a low level at a time of T0, and thus the switchS1 is turned-off and the capacitor C2 starts to be charged. Then, themulti-voltage VM starts to be increased from the time of T0.

When the multi-voltage VM reaches the first threshold voltage VTH1 at atime of T1, the first comparison signal CM1 is a high level and theinverted comparison signal CMB1 is a low level.

When the multi-voltage VM reaches the reference voltage of 1.5 V at atime of T2, the signal VMS is a high level, and thus the output of theAND gate 101 is a high level. Then, the initialization signal INT as theoutput of the AND gate 105 is a high level at a time of T3, and thefirst counter 103 is enabled, and thus the counting operation starts.The D-flip-flop 18 is enabled by the initialization signal INT of a highlevel at the time of T3, and thus the output signal MR is a high level.The gate voltage VG as the output of the OR gate 17 is a high level, andthus the switch S2 is turned-on. Then, the capacitor C2 is discharged bythe current ID of the sink current source 12, and thus the multi-voltageVM starts to be decreased from the time of T3.

When the multi-voltage VM is a voltage that is smaller than the firstthreshold voltage of 1 V at a time of T4, the first comparison signalCM1 is a low level and the inverted comparison signal CMB1 is a highlevel. The D-flip-flop 18 is reset at the time of T4, and thus theoutput signal MR is a low level and the inverted output signal MRB is ahigh level. Then, the gate voltage VG is a low level, and theD-flip-flop 19 is enabled, and thus the output signal DQ1 is a highlevel. The switch S2 is turned-off by the gate voltage VG of a low leveland the multi-voltage VM starts to be increased.

When the multi-voltage VM reaches the first threshold voltage VTH1 at atime of T41, the first comparison signal CM1 is a high level and theinverted comparison signal CMB1 is a low level. Then, all inputs of theAND comparator 20 are a high level, and thus the first count enablesignal CE1 is a high level.

When the multi-voltage VM reaches the second threshold voltage VTH2 at atime of T5, the second comparison signal CM2 is a high level and theD-flip-flop 19 is reset, and thus the output signal DQ1 is a low level.Then, the first count enable signal CE1 is a low level. An AND gate 23performs a logical AND operation of an inverted first count enablesignal CE1 and a signal obtained by delaying the first count enablesignal CE1 to generate the first register read signal RR1 of a highlevel at the time of T5. Since the signal obtained by delaying the firstcount enable signal CE1 is decreased to a low level after the delayperiod of the delay unit 22, the AND gate 23 generates the firstregister read signal RR1 of a low level after the delay period. Thedelay period according to the embodiment may be set so as to generatethe first register read signal RR1 as a short pulse.

The counter 31 stores the count signal CNT inputted through a pluralityof input ends D0-Dn according to the first register read signal RR1, andoutputs first dead time information PSD through a plurality of outputends Q0-Qn.

The delay unit 24 delays the first register read signal RR1 by the delayperiod, and outputs a count reset CR as a high level pulse at a time ofT6. The second counter 30 rests the count signal CNT according to thecount reset CR at the time of T6.

The D-flip-flop 25 is enabled by the count reset CR at the time of T6 tooutput the second count enable signal CE2 of a high level. The OR gate29 outputs a high level according to the second count enable signal CE2at the time of T6, and the count 30 is enabled by the output of the ORgate 29 to start a counting operation.

Meanwhile, the D-flip-flop 28 is enabled by the first register readsignal RR1 at the time of T5, and outputs the multi-discharge signal MDat a high level at the time of T5. The OR gate 17 outputs the gatevoltage VG of a high level according to the multi-discharge signal MD ofa high level, and the switch S2 is turned-on. Then, the capacitor C2 isdischarged by the current ID of the sink current source 12, and thus themulti-voltage VM starts to be decreased from the time of T5. Since themulti-voltage VM starts to be decreased from the time of T5, the secondcomparison signal CM2 has a pulse waveform where a pulse is increased toa high level at the time of T5 and then reduced to a low level.

When the multi-voltage VM is smaller than the first threshold voltageVTH1 at a time of T7, the inverted comparison signal CMB1 is increasedto a high level. The D-flip-flop 25 is reset by the inverted comparisonsignal CMB1. The second count enable signal CE2 is decreased to a lowlevel at the time of T7.

An AND gate 27 performs a logical AND operation of an inverted secondcount enable signal CE2 and a signal obtained by delaying the secondcount enable signal CE2 to generate the second register read signal RR2of a high level at the time of T7. Since the signal obtained by delayingthe second count enable signal CE2 is reduced to a low level after thedelay period of the delay unit 26, the AND gate 27 generates the secondregister read signal RR2 of a low level after the delay period. Thedelay period according to the embodiment may be set so as to generatethe second register read signal RR2 as the short pulse.

The counter 32 stores the count signal CNT inputted through a pluralityof input ends D0-Dn by the second register read signal RR2, and outputssecond dead time information SSD through a plurality of output endsQ0-Qn.

Meanwhile, the D-flip-flop 28 is reset by the second register readsignal RR2 at the time of T7, and outputs the multi-discharge signal MDat a low level at the time of T7. Since both two inputs of the OR gate17 have a low level, the OR gate 17 outputs the gate voltage VG of a lowlevel, and the switch S2 is turned-off. Then, the capacitor C2 ischarged by the current supplied by the bias voltage VB after the time ofT7, and thus the multi-voltage VM starts to be increased. Since themulti-voltage VM starts to be increased from the time of T7, the firstcomparison signal CM1 has a pulse waveform where a pulse is decreased toa low level at the time of T7 and then increased to a high level. On thecontrary, the inverted comparison signal CMB1 has a pulse waveform wherea pulse is increased to a high level at the time of T7 and thendecreased to a low level.

The output of the output end Dn of the first counter 103 is increased toa high level at a time of T9. The corresponding output end of aplurality of output ends D0-Dn may be determined according to theinitialization period. The SR latch 104 generates the initialization endsignal INTEND of a high level and the inverted output signal QB of a lowlevel according to the output of the output end Dn. The AND gate 105generates the initialization signal INT of a low level according to theinverted output signal QB of a low level. As shown in FIG. 4, theinitialization signal INT is maintained at a high level during theinitialization period.

After the initialization period, the multi-voltage VM is maintained at asteady state level. In the embodiment, the diode D1 is connected betweenthe bias voltage VB and the capacitor C2, and thus the steady statelevel of the multi-voltage VM increased by charging of the capacitor C2is limited.

For example, when the bias voltage VB is 5 V and a forward voltage ofthe diode D1 is 0.3 V, the steady state level is limited to 4.7 V. Thethird threshold voltage VTH3 is set to 4.8 V, and thus the protectionmode signal PMS as the output of the comparator 16 has a low level.

Unlike this, when the diode D1 is not connected between the bias voltageVB and the capacitor C2, the steady state level may be a level that ishigher than the third threshold voltage VTH3, for example, 5 V. Then,the protection mode signal PMS as the output of the comparator 16 isincreased to a high level in a steady state of the multi-voltage VM.

As described above, the diode may or may not be connected to the outsideof the control circuit according to a protection mode required by auser. For example, when the protection mode signal PMS has a high level,the mode may be an auto-restart mode. When the protection mode signalPMS has a low level, the mode may be a latch mode.

The first dead time information, the second dead time information, theprotection modes, and the remote controlling can be obtained through thepin generated by the multi-voltage without any additional pins of anintegrated circuit of the switch control circuit according to theembodiment. The number of pins of the IC and the size of the IC may bereduced through the embodiment.

The period during which the multi-voltage is increased from the firstthreshold voltage to the second threshold voltage may be adjustedthrough a time constant based on the resistor R1 and the capacitor C2.That is, first dead time information may be adjusted through theresistor R1 and the capacitor C2.

Further, the period during which the multi-voltage is decreased from thesecond threshold voltage to the first threshold voltage may be adjustedthrough a current of the sink current source 12 together with the timeconstant based on the resistor R1 and the capacitor C2. That is, seconddead time information may be adjusted through the resistor R1, thecapacitor C2, and the sink current source 12.

Moreover, the steady state level of the multi-voltage may be adjustedaccording to whether the diode is connected between the bias voltage VBand the capacitor C2. That is, the protection mode may be set accordingto whether the diode is connected.

In addition, generation and removal of the multi-voltage may be adjustedby an on/off of the switch S1. That is, remote controlling may beadjusted by the switch S1.

While this embodiments have been described in connection with what ispresently considered to be practical embodiments, it is to be understoodthat the invention is not limited to the disclosed embodiments, but, onthe contrary, is intended to cover various modifications and equivalentarrangements included within the spirit and scope of the appendedclaims.

DESCRIPTION OF SYMBOLS

-   -   1: power supply device    -   Q1: first switch    -   Q2: second switch    -   20: transformer    -   30: gate driving circuit    -   SR1: first synchronous rectification switch    -   SR2: second synchronous rectification switch    -   10: switch control circuit    -   11, 13, 14, 15, 16: comparator    -   12: sink current source    -   17, 29: OR gate    -   18, 19, 25, 28: D-flip-flop    -   20, 23, 27, 101, 105: AND gate    -   22, 24, 26: delay unit    -   30: second counter    -   103: first counter    -   31: first register    -   32: second register    -   33: biasing circuit    -   100: initialization unit    -   21, 102: inverter    -   200: oscillator    -   300: protection circuit    -   400: driving signal generation unit    -   500: synchronous rectification controller    -   R1-R11: resistor    -   C1-C4, Cr: capacitor    -   Lr: inductor    -   D: diode    -   S1, S2: switch

What is claimed:
 1. A switch control circuit comprising: biasingcircuitry configured to generate a predetermined bias voltage at a firstpin; multi-voltage circuitry configured to sense a multi-voltage at asecond pin; a first resistor configured to be connected between thefirst and second pins; a first capacitor configured to be connected tothe second pin and to generate the multi-voltage based on a currentgenerated through the first resistor by the bias voltage; and remotecontrol circuitry to control the multi-voltage, the remote controlcircuitry comprising a switch to receive a remote control signal tocause the first capacitor to discharge the multi-voltage to ground,wherein the multi-voltage circuitry is configured to set, based on themulti-voltage, at least two selected from the group consisting of firstdead time information, second dead time information, and a protectionmode, and wherein the switch control circuit initializes when the remotecontrol signal is at a low level and the switch is turned off.
 2. Theswitch control circuit of claim 1, wherein the multi-voltage circuitryis configured to set at least two selected from the group consisting ofthe first dead time information, the second dead time information andthe protection mode based on counting at least one period in which themulti-voltage varies with respect to at least one threshold voltage. 3.The switch control circuit of claim 2, wherein the multi-voltagecircuitry is configured to: count a first period from when themulti-voltage increases from a first threshold voltage to a secondthreshold voltage; and set the first dead time based on the firstcounted period.
 4. The switch control circuit of claim 2, wherein themulti-voltage circuitry is configured to: count a second period fromwhen the multi-voltage decreases from a second threshold voltage to afirst threshold voltage; and set the second dead time based on thesecond counted period.
 5. The switch control circuit of claim 2, whereinthe multi-voltage circuitry is configured to set the protection modeaccording to a steady-state level of the multi-voltage.
 6. The switchcontrol circuit of claim 5, wherein in setting the protection mode themulti-voltage circuitry is to set the protection mode to an auto-restartmode or a latch mode.
 7. A method, comprising: initializing a switchcontrol circuit of a power supply; providing a bias voltage to a firstresistor; charging, through the first resistor, a capacitor in theswitch control circuit to generate a multi-voltage; discharging, using aswitch controlled by a remote control signal, the capacitor to ground;counting at least one period in which the multi-voltage varies withrespect to at least one threshold voltage; and setting, based on thecount of the at least one period, at least two selected from the groupconsisting of first dead time information, second dead time informationand a protection mode of the power supply, wherein the switch controlcircuit initializes when the remote control signal is at a low level andthe switch is turned off.
 8. The method of claim 7, wherein counting atleast one period comprises counting a first period from when themulti-voltage increases from a first threshold voltage to a secondthreshold voltage; and setting at least two of first dead timeinformation, second dead time information and a protection modecomprises setting the first dead time based on the first counted period.9. The method of claim 7, wherein counting at least one period comprisescounting a second period from when the multi-voltage decreases from asecond threshold voltage to a first threshold voltage; and setting atleast two of first dead time information, second dead time informationand a protection mode comprises setting the second dead time based onthe second counted period.
 10. The method of claim 7, wherein setting atleast two of first dead time information, second dead time informationand a protection mode comprises setting the protection mode according toa steady-state level of the multi-voltage.
 11. A power supply device,comprising: a first switch and a second switch coupled in series betweenan input voltage and a primary side ground; a transformer including: aprimary side wire coupled to the input voltage and a node between thefirst switch and the second switch; and at least one secondary sidewire; a first synchronous rectification switch to rectify a currentflowing through a first wire of a secondary side; a second synchronousrectification switch to rectify a current flowing through a second wireof the secondary side; and a switch control circuit including: biasingcircuitry configured to generate a predetermined bias voltage at a firstpin; multi-voltage circuitry configured to sense a multi-voltage at asecond pin; a first resistor configured to be connected between thefirst and second pins; a first capacitor configured to be connected tothe second pin and to generate the multi-voltage based on a currentgenerated through the first resistor by the bias voltage; wherein themulti-voltage circuitry is configured to set at least two of a dead timebetween switching of the first and second switches, a dead time betweenswitching of the first and second synchronous rectification switches,and a protection mode based on the multi-voltage, wherein themulti-voltage circuitry is configured to set the protection modeaccording to a steady-state level of the multi-voltage, and wherein insetting the protection mode the multi-voltage circuitry includes settingthe protection mode to an auto-restart mode or a latch mode.
 12. Thepower supply device of claim 11, wherein the multi-voltage circuitry isconfigured to set at least two of the dead time between switching of thefirst and second switches, the dead time between switching of the firstand second synchronous rectification switches, and the protection modebased on counting at least one period in which the multi-voltage varieswith respect to at least one threshold voltage.
 13. The power supplydevice of claim 11, wherein the multi-voltage circuitry is configuredto: count a first period from when the multi-voltage increases from afirst threshold voltage to a second threshold voltage; and set the deadtime between switching of the first and second switches based on thefirst counted period.
 14. The power supply device of claim 11, whereinthe multi-voltage circuitry is configured to: count a second period fromwhen the multi-voltage decreases from a second threshold voltage to afirst threshold voltage; and set the dead time between switching of thefirst and second switches based on the second counted period.